There’s a reason parolees fare better at morning hearings, than in the afternoon. Here’s the research behind why, if you’re thinking or deciding too much, you won’t be able to do either very well.

If you’re going to your parole hearing, do your best to see the judge as early in the day as possible.

advertisement

advertisement

That’s a lesson from an Israeli university study that followed 1,100 court decisions over the course of a year. Prisoners who appeared early in the day received parole about 70% of the time, while those that came late in the evening had less than 10% chance at landing parole.

Why? Judges, being human, were worn down by a day full of mental work. They had, as the New York Times reports, fallen victim to decision fatigue.

“Making decisions uses the very same willpower that you use to say no to doughnuts, drugs, or illicit sex,” says Roy F. Baumeister, co-author of Willpower: Rediscovering the Greatest Human Strength. Think of your pool of decision-making energy as a not-unlimited reservoir: You could make a wrong investment or hire in the afternoon because you held your tongue or hustled to a meeting in the morning. When you’ve been sapped of willpower, you’re too drained to not indulge.

Over at Co.Design, Mark Wilson recently wrote about how strenuous thinking leaves your body exhausted.

advertisement

The conclusion came from an experiment at the University of Kent: Two groups of subjects did one of two 90-minute tasks: either playing a mentally taxing computer game or watch a “neutral mood” documentary about Ferrari sportscars or trains. Afterwards, each subject was asked to hop on an exercise bike, pick a resistance level, and pedal as long as they could.

In nearly every case, the documentary watchers peddled longer than the game players. What’s maybe more interesting is the inference Wilson makes: that both the cognitively drained game players and the cognitively rested doc watchers chose the same level of resistance. This shows, it seems, that people have a tough time of self-monitoring for exhaustion: We don’t excel at fitting our workloads to our energy levels.

What’s the consequence? Decision fatigue seems to be the mental equivalent of hanger, that dreaded combination of hunger and anger. As decision after decision depletes your willpower, John Tierney, the Times writer, says you’ll eventually do one of two dumb things:

Act impulsively: Since you have no energy to think about consequences

Do nothing: Since you have no energy to agonize

In this way, if we don’t learn to manage our energy, we won’t be able to manage our decisions.

We can build that same sense of brand loyalty in ourselves, too: By becoming loyal to healthy tasks, they can become productive, fatigue-free habits. President Obama, as was revealed last year, hits the gym right at 7:30 every morning and only wears blue or gray suits, explaining that it focused his decision-making energy. And the best habits, Warren Buffett said last week, predict future success.

advertisement

But just as powerful–and probably far more subtle–is to develop a sense of how much your decisions have fatigued you and to bolster your energy supplies.

About the author

Drake Baer was a contributing writer at Fast Company, where he covered work culture. He's the co-author of Everything Connects, a book about how intrapersonal, interpersonal, and organizational psychology shape innovation.